You’ve probably heard of identical and fraternal twins, but a report published Thursday says there’s a third kind — sesquizygous twins or “semi-identical.”
Identical — or monozygotic — twins pop up from a single fertilized egg that eventually splits in two and forms two identical boys or two girls. They share 100% of their DNA.Fraternal — or dizygotic — twins form from two eggs that have been fertilized by two of the father’s sperm, producing two genetically unique siblings. They share 50% of their DNA.But “semi-identical” twins are so rare, experts say they have only identified two cases — ever.
https://edition.cnn.com/2019/02/28/health/rare-twins-semi-identical-australia-trnd/index.html
